Enhanced magneto-caloric effect upon fourth element (Cu, Fe, Co) substitution in Ni–Mn–Sn thin films

The effect of small amounts of fourth element X (Cu, Fe, Co) substitution on magnetic transition and magneto-caloric properties of Ni–Mn–Sn thin films has been investigated. The ternary and quaternary films show cubic L21 structure with room-temperature ferromagnetism after heat treatment. The Curie temperature of the film is close to room temperature which does not shift much upon X (Cu, Fe, Co) substitution. The variations in magnetic entropy change (ΔSM) and refrigeration capacity (RC) with Cu/Co substitution are very less. However, an enhancement in ΔSM and RC from − 3.85 × 104 erg/cc K (− 0.47 J/kg K) and 1.50 × 106 erg/cc (18.3 J/kg) to − 5.66 × 104 erg/cc K (− 0.69 J/kg K) and 2.50 × 106 erg/cc (30.4 J/kg) is observed with 3.6 at.% Fe substitution for a field change of 18 kOe. This shows that Fe is the ideal fourth element for enhancing magneto-caloric effect in Ni–Mn–Sn thin films.